Audi 80/Avant (B4)
since 1991-1995 release
Repair and operation of the car
+ Technical specification
+ System of production of the fulfilled gases
+ Cooling system
+ Fuel tank and fuel pump
+ Air filter and airintaking channels
- System of injection
+ System of injection Mono-Motronic
- System of injection Digifant
Malfunctions and independent diagnostics
Check of separate elements
Removal of vpryskny nozzles
Check of the mode of idling and analysis of exhaust gases
List of malfunctions
+ System of injection KE-III-Jetronic
+ Systems of injection of MPI and MPFI
+ Transmission and transmission
+ Suspension bracket and steering
+ Brake system
+ Anti-blocking system of brakes
+ Wheels and tires
+ Body electrical system
+ System of ignition
+ Signaling devices
+ Devices and auxiliary devices
+ Heating and ventilation
+ Body elements
+ Search of malfunctions
System of injection Digifant
On this illustration the system of injection Digifant with its components is schematically presented. The way of air is shown by white shooters, supply with fuel is presented in red color.
Multipoint injectionThe system of injection in which each cylinder has own vpryskny nozzle, than that in which the injection is made only by one central nozzle is suitable for perhaps more exact distribution of mix of fuel/air better. Therefore the 85 Kw engine is supplied with the multipoint (distributed) system of injection. It is about electronically the operated system with the programmed characteristic of injection, with the operated system of ignition, with the ignition moment regulated on a detonation, with the integrated stabilization of frequency of rotation in the mode of idling and with interruption in supply of fuel in the mode of compulsory idling.
To whom the name of this system of injection is reminded by the word "Elefant" (elephant), that is near from the truth at all. Electronics engineers of Volkswagen and Audi took this name from "a white elephant" (weiber Elefant) – among programmers so call Jacks of all trades. New word formation – Digitaler Elefant.
The control unit receives via the multicontact plug the following types of information from:
On the basis of information on the frequency of rotation and loading the control unit counts duration of opening of electromagnetic vpryskny nozzles and by that injectable amount of fuel. For this purpose characteristics of injection and in addition the characteristic of ignition are at the disposal of the control unit. These characteristics represent a collection of data for various situations at operation of the engine and the corresponding amounts of fuel, and also the ignition moments. These indicators the control unit can change after receipt of so-called adjustment signals (for example temperatures of inlet air and cooling liquid).
Two butterfly valves are in a branch pipe in an inlet collector. Smaller of these gates it is connected by a cable of the drive of "gas" with a pedal in salon. It doses a stream of inlet air in the engine. If the pedal of an accelerator is squeezed out stronger, then draft opens the second, big gate, in the provision of full "gas" both gates are open.
Potentiometer of a butterfly valve
The potentiometer of a butterfly valve covers the provision of a butterfly valve from "idling" at present (the butterfly valve is closed) to "full loading" (the butterfly valve is completely open). On the basis of its information idling stabilization, interruption in supply of fuel in the mode of compulsory idling or enrichment of gas mixture at full opening of a butterfly valve is activated.
It is located in front of the distributor of fuel and regulates pressure of supply of fuel to vpryskny nozzles. For this purpose it obtains information on a condition of depression in an inlet collector. At the closed butterfly valve and high depression it keeps lower pressure in the idling mode. At decrease in depression at bigger loading of the engine the regulator of pressure increases fuel supply pressure. The fuel pump gives fuel with more high working pressure, but thanks to the regulator of pressure of plums of gasoline back in the fuel tank respectively increases or, if necessary, decreases.
At each turn of a bent shaft they inject gasoline in vpryskny the channel in front of the inlet valve of the corresponding cylinder – duration of this process defines the control unit. The corresponding cylinder receives one portion for emergency, and the second at the open inlet valve directly in the combustion chamber.
The sensor of temperature of the arriving air
It is located sideways in a flowmeter of air and thus can precisely determine temperature of the arriving air. Temperature of inlet air gets to the control unit in the form of resistance indicator. This indicator is necessary for an optimum dosage of fuel.
Sensor of temperature of cooling liquid
Temperature of cooling liquid is necessary for management of many functions of injection: enrichment of starting mix, poststarting enrichment (on all range of temperatures), enrichment at acceleration and shutdown of supply of fuel in the mode of compulsory idling (the movement by a setup). Information on temperature of cooling liquid comes to the control unit also in the form of resistance indicator. The control unit counts the necessary duration of injection which at the engine warmed up to the working temperature is in range between two and eight milliseconds. This indicator can increase to 70% if temperature of cooling liquid reaches –25 °C.
The air, necessary for combustion, arriving from the air filter, more or less (depending on the let-in quantity) wrings out a valvate lock in an air flowmeter aside, at the same time the attenuation valve connected with a valvate lock prevents fluctuations of a valvate lock. The potentiometer sends to the control unit depending on the provision of a valvate lock a signal in the form of tension: high voltage at full discovery and a large amount of air, small tension at small opening.
Starting fuel valve
This vpryskny nozzle with the electromagnetic drive injects in vpryskny the collector additional amount of fuel during 1 — 4 with depending on engine temperature at start. Duration of injection defines the control unit of system of injection Digifant.
Idling stabilization valve
In a warming up phase, at full turn of the amplifier of the steering mechanism, at the working conditioner or at the included step of the automatic transmission this valve frees the additional air canal, bypassing thereby a butterfly valve.
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